1. Field of the Invention
The present invention generally relates to a formation method of conductive bumps. In particular, the present invention relates to a formation method of conductive bumps by a screen printing method.
2. Description of the Prior Art
FIG. 1A to FIG. 1C are schematically diagrams illustrating the formation of conductive bumps in accordance with a prior art. Referring to FIG. 1A, a semiconductor device 101, such as a silicon wafer including a passivation layer, a bonding zone 103 and a dielectric layer 105A. The bonding zone 103 in an opening 105B is implemented by the partial removal of the dielectric layer 105A. FIG. 1C is a top-view diagram with respect to FIG. 1A, in which the bonding zone 103 exposed by the opening 105B is a whole bulk area.
Next, Referring to FIG. 1B, conductive material 109 is filled into the opening 105B to cover the bonding zone 103. The conductive material 109, such as a solder material, is filled into the opening 105B with the help of a screen printing technology. However, if the excess conductive material 109 would be scraped off after the step of screen printing, the conductive material 109 on the bonding zone 103 is possible to be scraped off to result in a recess surface on the opening 105B. The condition of the recess surface is serious with the increase of the dimension of the opening 105B. Accordingly, it is important to prevent both the short of and uniform distribution of the conductive material for the formation of conductive bumps.